PARIS — Police are searching for a 5-year-old British boy with a severe brain tumor whose parents took him out of a British hospital and were last seen in France.

The press office for Jehovah’s Witnesses said Friday that Ashya King’s parents were followers, but that there was no indication that the family’s decision was motivated by religious convictions.

Interpol said it was seeking information on the boy’s whereabouts. The family was believed to be in France. Parents Brett King, 51, and Naghemeh King, 45, removed the boy Thursday from Southampton General Hospital in Britain and took a ferry to France with their gray Hyundai and the boy’s six siblings, the international police body said.

French Prosecutor Eric Bouillard of Cherbourg, where they were last seen, said authorities opened an investigation for suspected kidnapping and “failure to carry out parental duties.”

The Hampshire police website said the boy was likely to be in a wheelchair or pushchair, can’t communicate verbally, and is immobile.

“If we do not locate Ashya today there are serious concerns for his life,” said Det. Supt. Dick Pearson, a Hampshire police investigator, in an Interpol statement. “He is receiving constant medical care within the U.K. due to recent surgery and ongoing medical issues.”

“Without this specialist 24-hour care, Ashya is at risk of additional health complications which place him at substantial risk,” he said.

Authorities in France and Britain set up telephone hotlines to take in tips from the public.

“It’s a race against time,” said Pierre-Henry Brandet, the French Interior Ministry spokesman. He said it was unclear whether the child was still in France, and said the couple’s final destination could be another country.

The press office for Jehovah’s Witnesses said it wasn’t aware of the facts of the case, but said Jehovah’s Witnesses are encouraged to seek the best medical treatment for themselves and their children.

Jehovah’s Witnesses accept medical treatment, but believe the Bible forbids some treatments and they often refuse blood transfusions.